Australia not involved in strikes on Syria but supports ally US

Australia is standing by its longtime ally as US President Donald Trump announced a series of precision strikes against the Assad regime in Syria.

Mr Trump announced a combined operation with Britain and France to target Syrian President Bashar al-Assad's chemical weapons capabilities after a poison gas attack killed at least 60 people in Douma last week.

"The use of chemical weapons by anyone, anywhere, under any circumstances is illegal and utterly reprehensible," Prime Minister Malcolm Turnbull said.

"The Assad regime must not be allowed to commit such crimes with impunity."

Damascus sky lights up with service to air missile fire as the US launches an attack on Syria. (AAP) (AAP)

The strikes were "a calibrated, proportionate and targeted response."

Mr Turnbull criticised Russia for its veto of a UN Security Council resolution this week that sought to respond to reports of chemical weapon attacks.

"It is tantamount to Russian support for such attacks," Labor leader Bill Shorten said in a joint statement.

"The international community must redouble its efforts towards a political solution to the conflict in Syria."

Defence Minister Marise Payne spoke to US Secretary of Defence James Mattis this morning for a briefing on the three targets of the strike.

"It has reduced the regime's ability to use chemical weapons in the future and sends a clear and strong message that the use of chemical weapons will not be tolerated by the international community," Ms Payne told reporters.

She assured reporters no request for support had been made and there had been no Australian involvement in the strikes.

"Australia's mission in Iraq and Syria is the defeat of Daesh," she said.

The attack in Syria last week. (AP/AAP)The attack in Syria last week. (AP)

For the federal Greens, the actions were cause for Australia to rethink its US alliance.

"Donald Trump is an unpredictable and dangerous ally. A quick glance at his recent tweets shows this is a cynical political exercise for him and he cannot be trusted to avoid the dangers of escalation and miscalculation."

In a televised address, Mr Trump said the US was prepared to sustain its response until the Syrian regime stopped its use of chemical weapons.

"These are not the actions of a man, they are crimes of a monster," President Trump said of the attack in Douma last week.

"The purpose of our actions tonight is to establish a strong deterrent against the production, spread and use of chemical weapons."

Three confirmed targets were struck: a scientific research centre near Damascus, a chemical weapons storage facility west of Homs and a chemical weapons facility serving as a command post.

Meanwhile, the Syrian Army said the strikes will not diminish the army's fight against all remaining militants in the country.

The US, Britain and France struck Syrian military targets before dawn over a suspected gas attack last week, which Western powers blamed on Syrian President Bashar al-Assad and his allies.

The army said nearly 110 missiles hit targets in the capital Damascus and other territory, and air defence systems brought most of them down.

"Such attacks will not deter our armed forces and allied forces from persisting to crush what is left of the armed terrorist groups," the military said.

Syrian President Bashar al Assad is accused of conducting chemical attacks against his own people, but is supported by Russian President Vladimir Putin. (AAP)

Damascus with key allies Russia and Iran have lambasted reports of the suspected gas attack as bogus. The Syrian government has accused Washington of seeking to use it as a pretext for attacking.

The foreign ministry said earlier that the US-led strikes would only "lead to inflaming tensions in the world" and threaten international security.

"The barbaric aggression ...will not affect in any way the determination and insistence of the Syrian people and their heroic armed forces," state media cited an official source in the ministry as saying.

It is the first time as prime minister that Theresa May has committed British armed forces to combat.

"It is not a decision I have taken lightly," she said.

"We cannot allow the use of chemical weapons to become normalised, within Syria in the streets of the UK or anywhere else in the world."

As the leaders spoke, explosions were heard in Damascus.

A Reuters witness heard a series of loud blasts in the Syrian capital early today.

But Russia's Defence Ministry said the majority of missiles fired were intercepted by Syrian government air defence systems.

Amnesty International Australia spokeswoman Diana Sayed called on the government to pursue a solution backed by the international community.

"Australia must call on its allies carrying out these attacks to make the protection of civilians their utmost priority, and to take extra caution as these strikes have not been approved by the United Nations," she said.